Magnetic hard disk drives (HDDs) have been employed in information technology as a low-cost means for providing random access to large quantities of data. As the need for data storage has expanded, the areal density of information stored in HDDs has been continuously increased. In addition to high storage capacity, the ability of an HDD to access stored data quickly is also important. To meet the ever-increasing requirements for high access performance and faster throughput, HDDs have been configured with multiple rotary actuators and associated read/write channels that are designed to operate simultaneously. Thus, each rotary actuator enables the independent positioning of one or more magnetic heads for reading and writing data, thereby greatly increasing the throughput of such HDDs.
One drawback to the use of independent rotary actuators is that the mechanical interaction between such actuators can affect positioning accuracy of a magnetic head that is associated with one actuator when another actuator is in motion. For example, when one actuator is seeking to a data track on a first disk surface, the high accelerations and changes in acceleration of the actuator can generate vibrations which will significantly affect the positioning accuracy of the magnetic head of another actuator while the other actuator is track following a target data track on a second disk surface.
In some instances, vibrations from one actuator can alter the position of the magnetic head of a track-following actuator to the point that an off-track error occurs, and the magnetic head can no longer read data from or write data to the target data track on the second disk surface. In such instances, a portion of the target data track is not successfully accessed, and an additional revolution of the second disk surface must occur so that the magnetic head can read data from or write data to the portion of the target data track not successfully accessed. Thus, when off-track errors occur with relative frequency, significant delays in completing disk access operations occur, which reduces the normally greater throughput of a multi-actuator HDD.
Consequently, there is a need in the art for efficiently recovering from off-track errors that occur in an HDD, particularly in a multi-actuator HDD.